THE NERC MST RADAR FACILITY AT ABERYSTWYTH
Only limited support can be provided for MST radar data products derived from earlier versions of the signal processing (see below). Users are therefore strongly encouraged to make use of version-3 processed data wherever possible. This does not apply to the raw radar data (IQ and Doppler spectra), for which only version 0 data are available. Please contact the NERC MST Radar Facility Project Scientist if you are having difficulties finding the data products you need.
- Use the following links to find out more about:
- Data archiving conventions
- File naming conventions
- File contents
- File naming conventions
Although gradual changes have been made to the MST radar signal processing since the radar began operations in 1990, these changes have not been documented and the people responsible for them have now retired. Therefore all data stored in the original file formats have been retrospectively classified as version-0 products.
The signal processing makes use of a number of non-standard product definitions and simplifying assumptions, which were largely necessary in order to allow real-time processing using 1990-vintage computer technology. No explicit reliability flagging is used in these files, although the processing is robust and the data are typically good under suitable signal-to-noise conditions. The data products are spread across a number of different files, all of which use non-standard formats (both ASCII and binary) and for which only limited documentation exists. Follow the file format pages for further information.
The averaged data products represent 12 minute time averages (typically 3 - 5 cycles of observation). This can obscure small scale features such as turbulence and gravity waves. The ASCII versions of the 12 minute averaged files have not been produced since May 2004.
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Data product | |
BADC location | |
File prefix | |
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| Unaveraged wind data | /badc/mst/data/mst-products-v0/vw | vh | File format | |||||
| Unaveraged radial data | /badc/mst/data/mst-products-v0/rw/ | rw | File format | |||||
| Averaged wind data | /badc/mst/data/mst-products-v0/vector/ | vcf, vec | File format | |||||
| Averaged power data | /badc/mst/data/mst-products-v0/power/ | pwf, pwr | File format | |||||
| Averaged radial data | /badc/mst/data/mst-products-v0/radial/ | rad, rdf | File format |
DEPRECATED: Version-1
Version-1 data products are primarily available for the period June 2003 - December 2004. A key feature of the new products is the use of standard (NASA-Ames) format (ASCII) files. These make the data much easier to read and to understand. There are only 2 types of version-1 data products, both of which represent unaveraged data. The radial files are very similar to those from the version-0 (unaveraged) processing. The Cartesian files contain wind data, tropopause altitude and sharpness information and a number of radar return parameters (signal power,aspect, spectral width and beam-broadening corrected spectral width) on a regular grid. It is not necessary to know much about the way in which the radar operates in order to make use of the data from these files and they are recommended for most purposes. Follow the file format links for full details of the file contents.
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Data product | |
BADC location | |
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| Radial data | /badc/mst/data/mst-products-v1/radial/ | File format | ||||
| Cartesian data | /badc/mst/data/mst-products-v1/cartesian/ | File format |
The version-1 signal processing makes use of a time-continuity algorithm for reliability flagging. Initially the strongest signal within each Doppler spectrum is assumed to be the desired one, and the reliability flagging subsequently removes outlying data points. For the most part this has proved to be very effective, particularly in regions of low signal-to-noise ratio. This means that the maximum useful altitude for wind-profiling purposes (in the ST mode) is typically between 17 and 20 km, as opposed to between 15 and 17 km for the version-0 (unaveraged) processing. However, there are 3 known problems with the data:
- Under conditions of fast low-level winds, the strength of ground
clutter signals can exceed that of the atmospheric returns at
certain altitudes - notably at around 2.5, 3.0 and 7.0 km. Since
these ground clutter signals tend to persist over many hours, they
are accepted by the time-continuity algorithm as desired
signal. They give rise to narrow horizontal bands of low-wind-speed
in the quick-look plots. This problem does not affect version-0 data
products
Click here for an example of this problem.
- There are sporadic periods of what appears to be radio frequency
interference. The strength of these signals is approximately
constant as a function of altitude and typically exceeds that of the
atmospheric signals at altitudes above 10 km. Since these signals
persist for the order of a few hours, they are again accepted by the
time-continuity algorithm as desired signal. They give rise to
narrow vertical bands of clearly anomalous wind data in the
quick-look plots. This problem also affects version-0 data
products.
Click here for an example of this problem.
- Under relatively rare conditions of heavy precipitation, the
strength of hydrometeor returns can exceed that of the (desired)
clear-air returns at low altitudes. Sometimes the downward
velocities of the hydrometeors are so large, and persist for such a
short time, that the signals are rejected by the time-continuity
algorithm. However, in the altitude regions where the hydrometeors
are just beginning to accelerate downwards, the signals can be
accepted. Sometimes both the hydrometeor and clear-air returns are
identified as belonging to a single, broad signal. Either way this
sort of contamination tends to give rise to large downward vertical
velocities and enhanced spectral widths in the quick-look
plots. This problem also affects version-0 data products.
Click here for an example of this problem.
Version-2 processing is essentially the same as that used for version-1. The only difference is that it makes use of the complementary beam horizontal velocity variability information (also available in version-1 files) to provide additional reliability flagging. This has proved to effective at removing data contaminated by the 3 problems noted above. This leads to more gaps in the data. Since Version-2 data products are also written in NASA-Ames format files, they can be read by routines written for version-1 products after making a few very small modifications. Version 2 data products are available for the entire observation archive until the end of 2006. New files will cease to be available when a new data acquisition system is installed in early 2007.
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Data product | |
BADC location | |
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| Radial data | /badc/mst/data/mst-products-v2/radial/ | File format | ||||
| Cartesian data | /badc/mst/data/mst-products-v2/cartesian/ | File format |
CURRENT: Version-3
An improved, multiple-signal-component processing scheme has been under test, in collaboration with the Met Office, since January 2006. The quality of the thirty-minute-average wind-profile data is measurably better than that of v0 data and the Met Office switched over to v3 data for operational assimilation in September 2006. More details about the processing scheme, together with statistical measures of the wind-profile data quality, are available here.
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Data product | |
BADC location | |
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| Radial data - ST-mode | /badc/mst/data/mst-products-v3/st-mode/radial/ | File format | ||||
| Radial data - M-mode | /badc/mst/data/mst-products-v3/m-mode/radial/ | File format | ||||
| Cartesian data - ST-mode | /badc/mst/data/mst-products-v3/st-mode/cartesian/ | File format | ||||
| Cartesian data - M-mode | /badc/mst/data/mst-products-v3/m-mode/cartesian/ | File format |